The present invention relates to a pressing apparatus for pressing a workpiece placed in a slightly inclined state against a target portion with uniform force, for example, and more specifically to an automatic aligning pressing apparatus for uniformly pressing a workpiece such as a semiconductor chip placed on a slightly inclined plane or the like against a target portion by automatically aligning a head for pressing.
An automatic aligning pressing apparatus for pressing a workpiece placed on a slightly inclined plane or the like against a target portion with uniform force by automatically aligning a head for pressing is already known.
This type of pressing apparatus generally includes an air bearing having a bearing surface in a shape of a partial recessed spherical surface and an aligning member having a borne surface which is in a shape of a partial projecting spherical surface and which is fitted with the bearing surface and the pressing head for pressing the workpiece is mounted to the aligning member. The aligning member is floated by supplying air between the bearing surface and the borne surface. By pressing the workpiece with the pressing head in this state, the aligning member and the pressing head are automatically aligned according to inclination of the workpiece, thereby uniformly pressing the workpiece against the target position.
Such a pressing apparatus has a lock mechanism for pressing and locking the aligning member after alignment against and to the air bearing. The prior-art lock mechanism presses and locks the aligning member against and to the air bearing by evacuating a gap between the bearing surface and the borne surface. However, it is necessary to increase surface areas of the bearing surface and the borne surface to ensure required suction force in the locking by means of evacuation. Therefore, a size of the apparatus increases adversely.
It is an object of the present invention to provide a small-sized aligning pressing apparatus with low air consumption by which an aligning member can be automatically aligned by floating the aligning member and the aligning member can be locked in an aligned position by mechanical means.
To achieve the above object, an automatic aligning pressing apparatus of the invention comprises: an apparatus main body to be mounted to an automatic device; an air bearing mounted to the apparatus main body and including a bearing surface in a shape of a partial recessed spherical surface at a tip end of the air bearing; an aligning member which includes a borne surface in a shape of a partial projecting spherical surface having the same curvature as the bearing surface of the air bearing and a head mounting face to be mounted with a pressing head for a workpiece and which is supported by the air bearing with the borne surface fitted with the bearing surface; an air supply flow path for supplying compressed air to the bearing surface of the air bearing to float the aligning member from the air bearing; a lock mechanism for pressing and locking the aligning member against and to the bearing surface of the air bearing; and a cylinder driving portion for driving the lock mechanism, wherein the lock mechanism has a piston rod which passes through the air bearing and the aligning member in a position of central portions of the bearing surface and the borne surface in a freely inserted state and which is moved forward and rearward by the cylinder driving portion, a flange-shaped locking portion formed at a tip end of the piston rod, a depression which is formed in the aligning member and in which the locking portion is fitted, and contact faces in shapes of partial spherical surfaces which are formed at the locking portion and the depression to come in contact with each other in locking, and the contact faces are formed concentrically with the borne surface.
In the automatic aligning pressing apparatus with the above structure, if the piston rod is moved forward by the cylinder driving portion, a gap of about 0.02 to 0.05 mm is created between the bearing surface of the air bearing and the borne surface of the aligning member, compressed air is supplied into the gap from the air blowoff hole in the bearing face, and the aligning member is retained in a floating state by an air film. If the pressing head mounted to the aligning member is pressed against the workpiece in this state, because the borne surface and the contact face of the aligning member are concentric with each other, the aligning member is automatically aligned along an inclined face of the workpiece if the workpiece is slightly inclined and the workpiece is uniformly pressed against a target portion.
If the piston rod is drawn back by the cylinder driving portion, the contact face of the locking portion at the tip end of the piston rod comes in contact with the contact face of the aligning member, the aligning member is pressed against the bearing surface of the air bearing, and the aligning member that has been floating is smoothly locked to the air bearing in the aligned position.
By mechanically locking the aligning member through the piston rod by using the cylinder driving portion as described above, it is possible to reduce a size of the pressing apparatus as compared with a prior-art locking method by evacuation and air consumption also reduces.
In the invention, centers of curvature of the bearing surface of the air bearing, the borne surface of the aligning member, and the contact faces of the locking portion and the aligning member are set at a center of a workpiece pressing face of the pressing head mounted to the aligning member. As a result, it is possible to carry out the above floating further stably.
In the invention, it is preferable that the apparatus main body includes in a front end face thereof a depression, the air bearing is fixed to the apparatus main body in the depression, the aligning member is supported by the air bearing, a labyrinth for drawing air and communicating with a gap between the bearing surface and the borne surface is provided between outer peripheral faces of the air bearing and the aligning member and an inner peripheral face of the depression, and the labyrinth communicates with a port for recovering air. As a result, it is possible to recover the compressed air after the compressed air is used for floating the aligning member. Thus, discharge of dust to the surrounding environment can be suppressed and use of the apparatus in a clean room is possible.
In the invention, the air supply flow path extends from a supply port formed in the apparatus main body to pass through a connecting portion between the apparatus main body and the air bearing and to communicate with the blowoff hole opening in the bearing surface and sealing means for preventing air leakage from the connecting portion is provided to the connecting portion. By providing such sealing means, it is possible to reduce the amount of air consumption and to increase burden of the air bearing.
In this case, it is preferable that the sealing means is a heat-resistant annular sealant made of fluoro rubber and the sealing means is inserted into each of an outer peripheral annular groove and an inner peripheral annular groove formed in either one of connecting faces in the connecting portion between the apparatus main body side and the air bearing. As a result, it is possible to use the automatic aligning pressing apparatus even in a high-temperature environment.
It is preferable that the invention further comprises biasing means for applying operating force toward the air bearing side to the aligning member in floating. The biasing means is formed of a magnet, for example, and the aligning member formed of a magnetic substance can be attracted toward the air bearing side by the magnet.
It is preferable that the invention further comprises a rotation preventing mechanism for preventing rotation of the aligning member with respect to the air bearing. The rotation preventing mechanism may be formed of a pin fixed to one of the air bearing and the aligning member and a pin hole which is formed in the other of the air bearing and the aligning member and in which the pin is fitted with a gap around the pin. It is preferable that an elastic body surrounding the pin is disposed in the pin hole.